Generally speaking, in the prior art solutions, the drawback relating to efficiency and reliability is tackled by installing accumulation systems between one unit and another, so as to avoid the need for connecting the units to each other by positive control of the objects transferred from one unit to another (indeed, in that case, the units are always in step with each other). Thus, stopping one of the units does not involve stopping the entire line.
These accumulation systems, however, are to the disadvantage of line hygiene.
In this regard, patent WO2009127962 to the same Applicant as this invention discloses a system which comprises a parison moulding machine, an oven for the parisons and a blow-moulding machine. The system also comprises a cooling carousel interposed between the moulding machine and the oven, and a storage system connected to the cooling carousel and to the blow-moulding machine.
This solution makes it possible to deal with certain critical situations, in particular the shutting down of the blow-moulding machine (in which case the moulding machine continues to make parisons which are transferred to the storage system) and the shutting down of the moulding machine (in which case the blow-moulding machine can continue to be fed with parisons from the storage system).
This solution, however, does not solve the problem of hygiene which is, in fact, made worse by the risk of the parisons getting dirty as they pass through the storage system.
In light of this, it should be noted that patent document IT1359024, in the name of the same Applicant as this invention, describes a storage system containing parisons and caps for feeding respective units of a bottling line. The interior of the storage system is kept under conditions of overpressure so as to allow storage of heterogeneous objects, that is, parisons and caps.
However, patent IT1359024, too, fails to deal with the problem of hygiene and does not provide solutions able to guarantee the reliability and efficiency of the line.
Moreover, it should be noted that even document WO2009127962 does not provide solutions able to guarantee the reliability and efficiency of an entire bottling line but proposes only a solution to the problem of the reliability (that is, of the uninterrupted service) of the subsystem consisting of the blow-moulder and the parison moulding machine.
In light of this, it should be noted that the following problems exist in connection with the efficiency of the line.
Moulding machines which process raw plastic (for example to mould the parisons or caps) have a high thermal inertia.
The high thermal inertia of the moulding units has two consequences.
The first consequence is that stopping the units too frequently can lead to problems. Indeed, the units need to be kept on all the time and the frequency of machine shutdowns must be reduced to a minimum.
The second consequence, linked with the first, is that these machines are designed to make objects (parisons or caps) of the same colour for relatively long periods of time (for example, some months). Since changing the colour of the plastic the objects are made of means, obviously, that the machine must be stopped, this must be done as infrequently as possible
Production requirements, however, make it necessary to change the colour of the bottles and caps more often (for example, weekly or fortnightly) than the colour change frequency recommended for the parison and cap moulding machines.
In light of this, the solutions adopted by the prior art for bottling lines tend to limit the efficiency of the line on account of the need to strike a compromise between the above mentioned opposite needs.